feat: render summarization/compact user message (#736)

src/cli/helpers/backfill.ts

@@ -5,7 +5,11 @@ import type {
   Message,
   TextContent,
 } from "@letta-ai/letta-client/resources/agents/messages";
-import { SYSTEM_REMINDER_CLOSE, SYSTEM_REMINDER_OPEN } from "../../constants";
+import {
+  COMPACTION_SUMMARY_HEADER,
+  SYSTEM_REMINDER_CLOSE,
+  SYSTEM_REMINDER_OPEN,
+} from "../../constants";
 import type { Buffers } from "./accumulator";
 
 /**
@@ -81,7 +85,7 @@ function truncateSystemReminder(text: string, maxLength: number): string {
  * Check if a user message is a compaction summary (system_alert with summary content).
  * Returns the summary text if found, null otherwise.
  */
-function extractCompactionSummary(text: string): string | null {
+export function extractCompactionSummary(text: string): string | null {
   try {
     const parsed = JSON.parse(text);
     if (
@@ -182,17 +186,12 @@ export function backfillBuffers(buffers: Buffers, history: Message[]): void {
         // Check if this is a compaction summary message (system_alert with summary)
         const compactionSummary = extractCompactionSummary(rawText);
         if (compactionSummary) {
-          // Render as a synthetic tool call showing the compaction
+          // Render as a user message with context header and summary
           const exists = buffers.byId.has(lineId);
           buffers.byId.set(lineId, {
-            kind: "tool_call",
+            kind: "user",
             id: lineId,
-            toolCallId: `compaction-${lineId}`,
-            name: "Compact",
-            argsText: "messages[...]",
-            resultText: compactionSummary,
-            resultOk: true,
-            phase: "finished",
+            text: `${COMPACTION_SUMMARY_HEADER}\n\n${compactionSummary}`,
           });
           if (!exists) buffers.order.push(lineId);
           break;